Under the auspices of the Society of General Physiologists, a symposium is planned for September, 1975, to explore the regulation of synthesis and turnover of specific functional membrane components in eucaryotic cells. Four interrelated areas will be discussed: (1) biogenesis and turnover of membrane macromolecules, including specific membrane components of such organelles as the plasma membrane and the membranes of phagosomes, lysosomes, mitochondria, chloroplasts, and the Golgi apparatus; (2) membrane genetics and the differentiation of functional components in specialized cell membranes; (3) the biochemical basis of functional membrane changes (especially in transport systems) in response to hormones; and (4) the biochemical basis of functional membrane changes in relation to growth control and malignant transformation. In each case, these processes are to be related to the cells' physiological state and metabolic requirements. We shall seek to have our speakers emphasize the nature of the signal, the cell receptors, and the known intermediate steps leading to the new functional state of the membrane. The program above will be conducted during four morning sessions. In conformity with past practices of the Society, we plan afternoon sessions of contributed papers many but not all of which will be related to the theme of the main symposium. Prompt (Spring 1976) publication of the invited papers by the Raven Press is planned.